A variety of heat sources may be cooled using a heat sink. A heat sink may be configured to dissipate heat to the surrounding environment. Some heat sinks may also include heat transfer elements such as radiators, fans, heat pipes, liquid cooling elements, phase-change cooling elements, and/or other features. A thermal interface material may be used to improve the thermal coupling between a heat source and a heat sink. The thermal interface material may be disposed between contact surfaces of the heat source and the heat sink at which heat is transferred.
Contact surfaces on the heat source or the heat sink may have variations caused by variations in materials and/or manufacturing processes. A thermal interface material may, for example, be used to fill gaps between the heat source and the heat sink occurring due to such variations. Such gaps, if not bridged by a thermal interface material, may decrease the thermal coupling between the heat source and the heat sink, thereby decreasing the efficiency with which heat may be transferred from the heat source to the heat sink.
One common form of thermal interface material is a heat-conductive paste or grease that is spread in a layer between the heat source and a heat sink. Pressure between the heat source and heat sink may cause the thermal interface material to spread from its initial position to cover the entire contact surface. A thermal pad, which may include a thermal paste or grease, may fill voids between the heat source and a heat sink. The thermal conductivity of many pastes or greases used as thermal interface materials is relatively low. For example, some commercially available thermal pastes or greases have a thermal conductivity value between 1.5 to 3λ, where λ is expressed in watts per meter kelvin (W/(m·K°)). In contrast, materials commonly used in heat sinks may have thermal conductivity values that are many times greater than such pastes or greases. For example, the thermal conductivity of aluminum is approximately 220λ, and the thermal conductivity of copper is approximately 390λ. The inventors of the present application have recognized that increasing the thermal conductivity of a thermal interface material may provide greater transference of heat and improved efficiency in certain applications.